Field of the Invention
The invention relates to rotating machinery spools and, particularly, to composite spools.
Description of Related Art
Spools are used in a great many types of rotating machinery to support rotating features of the machinery. One exemplary type of rotating machinery is gas turbine engines having spools such as rotors, drums, and disks. It is known to use composite spools for rotating machinery to reduce weight of the spools and the machinery. Composite rotors or disks for gas turbine engines are known in the art. Turbofan gas turbine engines generally include a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. Gas turbine engine rotors or disks generally have been manufactured of metallic materials usually as single items machined from a solid metal billet or as several elements welded together. Features machined into the metal disks and rotors include dovetail slots to receive dovetail roots of fan, booster, compressor, and turbine blades. Metal disks and rotors are relatively heavy. Metals have a lower specific strength and have very little inherent damping as compared to composite materials. The major benefit of composite spools such as disks and drums and rotors is to significantly reduce the weight and mass moment of inertia of the spool. While composites offer good strength and stiffness properties with respect to metals, they may lack robustness in tribological performance.
Composite integrally bladed rotors for use in gas turbine engines have been disclosed in several patents such as U.S. Pat. Nos. 4,747,900, 4,786,347, and 7,491,032. Composite integrally bladed rotors are subject to large forces which must be taken into account in designing the construction of the rotor to preserve its integrity. In the rotor disc, the major forces are exerted in circumferential directions so an ability to absorb hoop stress is important, whereas in the airfoil blades radially exerted forces predominate. Composite material used in such rotors typically include a resin (such as epoxy) which has low inherent strength. The composite material has a specific strength higher than that of metal due to the inclusion of fibers normally of the same material embedded in a matrix of the composite material. The fibers are known to be strongest in tension so the direction of the forces in the finished component will, at least in part, determine its strength. In some instances, the structural design of the component has been influenced by the need for fiber orientation.
It is highly desirable to have a design and method for manufacturing rotating machinery spools that are light-weight, strong, and robust.